The present invention relates to a degasifier for a liquid separated from a gaseous fluid in a gas/liquid separator in general, and more particularly for a degasifier forming part of a gseous fluid compressor system, for example for compressing atmospheric air.
In conventional systems for compressing a gaseous fluid, a liquid, such as oil, is used for cooling, lubricating and sealing the compressor, as for example a screw compressor, and is added to the gaseous fluid during compression of the gaseous fluid in the compressor portion of the system. The oil must be removed in a separating unit, prior to the gaseous fluid being delivered to the consumer. The separated liquid is returned to the compressor forming a part of the system, generally after having been passed through a cooler. The apparatus separating the liquid from the gaseous fluid is a gas/liquid separator, more particularly an oil-air separator in the specific example of a compressor system for air. The separator usually comprises a coarse separation section and a fine purification section. Both are installed in a vessel-like housing which is preferably of circular cylindrical shape. The gaseous fluid stream which enters the separator and which is to be processed consists of a mixture of liquid and gas, for example of a mixture of oil and air. The mixture is supplied to the inlet of the separator housing from the compressor outlet and is delivered, in the separator, against a baffle which constitutes the coarse separation section of the separator. The bottom portion of the housing forms a liquid collecting sump, i.e. an oil collecting sump, in which accumulates the oil separated from the gaseous fluid in the coarse separation section and in the fine purification section disposed downstream. The oil separated from the compressed air in the separator still contains air, in the form of bubbles. The oil, recovered in the separator, is returned to the compressor, and therefore, if it is desired to degasify the oil prior to returning it to the compressor, the degasifier operation is preferably effected in the oil collecting sump of the separator itself. The period of time during which the oil remains in the collecting sump has an important influence on the degasifying of the oil. Generally, it can be said that the period of time during which the oil remains within the collecting sump depends on the level of the oil in the collecting sump and on the operating pressure of the separator unit. However, as the oil is fed back to the compressor, the period of time during which the oil remains within the collecting sump can only be increased to a certain limit, and a longer time can only be achieved if the volume of oil flowing in the system is substantially increased. This, however, is undesirous for reasons of economy.
The proportion of gas in suspension in the oil fed back to the compressor has a strong influence on the overall efficiency of the compressor. The sealing effect of the oil in the compressor decreases as a function of the proportion of gas, in suspension in the oil, resulting in a loss of efficiency. In addition, the cooling effect of the oil in the compressor is substantially decreased and if a cooler is installed between the oil-air separator and the compressor, the heat transfer efficiency of the cooler is substantially decreased. Furthermore, measured in flow rate, the volume of oil returned to the compressor is reduced as a function of the volume of air entrained in the oil flow. In addition, the oil can no longer fulfil all the requirements for lubricating the moving parts of the compressor and the sound absorbing capability of the oil in the compressor is accordingly reduced such that the compressor is noisier.